|Astec Thermal Treatment Applications|
Astec remediation systems have been utilized for the treatment of soils and sediments containing a variety of different contaminants. In general, the higher the boiling point of the contaminant, the higher the temperature required for treatment.
Astec Thermal Remediation Systems treat soils and sediments containing various hydrocarbons ranging from gasoline and jet fuels to lubricants and heavy oils. Usually, heavier hydrocarbon contaminants require higher temperatures for treatment. Petroleum hydrocarbon contaminants are typically found at gasoline stations, fuel tank farms and depots, railroad maintenance yards, airports, and fuel spill sites resulting from transportation accidents. These types of remediation projects have been done by using both "on-site" and "off-site" approaches. Astec systems can be set-up at a central location, where contaminated materials are brought in from various locations.
Astec Indirect Thermal Recovery plants have effectively removed, recovered and recycled hydrocarbon contaminants. Oilfield wastes typically include tank bottoms, drill cuttings and oilfield sludges. High concentrations of petroleum products are typically contained in these wastes. Recovery of these contaminants can produce a recovered product which can have significant value in recycling. To recover these petroleum products, the Astec Indirect-fired thermal desorption processes can be used to separate a wide range of hydrocarbon type contaminants from soil, sludge and/or sediment, while condensing and recovering the contaminants. The air pollution control systems for these applications include scrubbers and condensers which are specifically designed for the type and concentration of the particular contaminated media to be treated. The arrangement of the components within these systems can vary depending upon the project parameters and feed material constituents.
Coal Gasification Sites
Astec direct-fired thermal desorption plants have effectively treated materials from many different manufactured gas plant (MGP) sites. Also known as TOWN GAS WORKS, these plants used a coal gasification process to manufacture fuel gas for lighting and heating. The by-product produced was a gas-processing residue. Many of these facilities generated large volumes of waste oil residues commonly referred to as COAL TARS which were buried in waste pits on-site and remained after the plants closed. Chemically, they primarily consist of polycyclic aromatic hydrocarbons (PAH's). These high-boiling point contaminants are effectively treated by using the Astec parallel flow rotary drum. The Astec parallel flow system has the inherent ability of achieving the best treatment standards for the fine materials which become airborne in the drum. This is possible because of higher temperature gas stream in a parallel flow PTU. Similar site contaminants that have been effectively treated by Astec plants include creosote and wood treating compounds from industrial processes which used coal, creosote and #6 fuel oil, or bunker fuel.
Pesticides are toxic compounds used for insect control which are very stable and under normal conditions will remain in the environment for years. Pesticide contamination is typically found where pesticides were manufactured, stored and/or applied. In general, pesticide contaminants have low vapor pressures and relatively low boiling/decomposition temperatures. These characteristics make these compounds well suited for thermal treatment to effectively remove them from soils. However, many of the contaminants contain chlorine, known as organo-chlorine pesticides. When chlorine is present, the destruction of these compounds will produce HCl as the compounds undergo thermal decomposition. An appropriate thermal treatment system therefore needs a means of controlling these acid gases. One such method involves the addition of a scrubber at the end of the process to control emissions of these acid gases. Thermal Desorption Systems with acid gas scrubbers have proven very effective. As a result, large volumes of pesticide contaminated soils have been treated in Astec Thermal Treatment Systems.
Other forms of recycling are being combined with the Astec Soil Remediation Process, including the treatment of municipal sludges, known as BIO-SOLIDS. The system shown at right utilizes a patented approach whereby sludge filter cake from the municipal wastewater treatment facility is introduced into the material cooling unit of a soil processing system. Here, it is heated to a predetermined temperature so that its pathogens are destroyed, but beneficial nutrients are maintained. After thorough mixing and pasteurization in the material cooling unit, the final soil-sludge product is discharged. The enriched product has enhanced material qualities and has been used for topsoil and potting soil.
Industrial Site Redevelopments
There are many closed industrial sites throughout the world that are being dismantled, remediated and redeveloped. In many cases, the properties have been sitting idle for years while the economic conditions evolve to the point that the value of the property in a redeveloped state outweighs the costs of the redevelopment. It is becoming common for these former industrial sites to be redeveloped for other uses outside of industry, including residential use and parkland. In many cases, regulatory issues also become a significant driver for redevelopment. Contaminants at these sites will vary widely depending on its former use and can include variations of hydrocarbon fuels, lubricants, solvents, chlorinated compounds, pesticides, agricultural contaminants, etc. Large quantities of contaminated materials at these industrial sites have been treated by Astec Thermal Remediation Plants. Many other sites are anticipated in the future.